1. Field of the Invention
The invention relates to a combined changeover contact-maker apparatus in which each of two systems of three phase and isolated switches having input and output terminals, is respectively associated with the mobile armature of one of two electromagnets able to be driven exclusively, reciprocal mechanical locking means being disposed between the mobile armatures so that each one, by its movement, prohibits that of the other, whereas first electric interconnection means are formed between the input terminals and the output terminals so as to cause changeover of two phases applied to a motor depending on whether one or other of the electromagnets is energized.
2. Description of the Prior Art
Such apparatus are very widely used in industry, particularly in that of lifting and handling appliances, for reversing the direction of rotation of the motor. Depending on the case, these apparatus comprise:
either two conventional contact-makers associated together and between which is disposed a mechanical locking case,
or two electromagnet systems mounted in the same casing and capable of moving the same set of mobile contact bridges in opposite directions between two sets of separate fixed contacts.
In the first case, the user must generally effect the mechanical association and himself provide the electric connection of 12 terminals.
In the other case, the positioning of a reciprocal locking means is not required, and the apparatus only has:
three terminals for the electric connection to the network and
three terminals for the electric connection to the motor,
which forms an advantage for the user.
If thermal and/or magnetic protection means are desired for the motor, the user must place in series an appropriate protection apparatus and this apparatus reacts appropriately to overloads, whatever the direction of rotation of the motor.
When it is desired to integrate two contact-makers and thermal protection means in one and the same case, several possibilities may be conceived.
According to one of these conceptions, based on the first case of mounting, a bulky assembly will be the result.
According to the other conception, the volume occupied will be slightly less.
In both cases, additional electric connections must be formed externally, either because of the arrangement of the terminals of the switches, or because of the opposed arrangement of the two electromagnets with respect to the switches.
Contact-maker apparatus are further known, which may be used for driving the multiphase motors in a single direction, including in the same case thermal and magnetic protection means as well as a means (manual or remote controlled) for locally resetting these protection means. Such an apparatus, which may be illustrated by the U.S. Pat. No. 4,495,538 of the assignee, is also protected against short circuit currents.
The prior existence of such apparatus might lead the user of a motor operable in two directions to an association comparable with that mentioned above; the presentation of the cases of these apparatus makes it however difficult to place mechanical locking means therebetween; in addition, the fact that, depending on the direction of operation, only one of the two thermal protection systems is engaged, makes illusory the protection which might have been hoped for because of the fact that each of the two bimetallic strip systems generally used for this purpose only gives an incomplete image of the thermal state of the motor.
The invention proposes consequently providing in the same case a changeover contact making apparatus which is reliably protected against small and extended overloads, against instantaneous overcurrents and against short circuit currents while being provided with mechanical locking means and a single resetting member and only having externally three terminals for connection to the network and three terminals for connection to the load; this apparatus will further offer the user the faculty of assocating with each of the electro-magnet armatures, at will and without any possible error, sets of appropriate auxiliary contacts in a sufficiently large number so that auxiliary signals generally desired for each of the directions may be developed in addition to those which are intended for the electric locking circuit of the coil currents of the contact-makers.